Instructions
Hook up your LAN system. You need to connect multiple PlayStation 3 entertainment consoles to a single router. Simply use Ethernet cables to connect the PS3s to the router. Make sure to connect each PS3 to a television.
Turn on all PS3s and televisions you wish to use. They will automatically appear on the same network through the use of your router.
Plug "Modern Warfare 3" into each machine. Turn the game on with each machine. Let the games boot. Go to "Multiplayer." Select "LAN party." You can now enjoy the game across the multiple consoles connected to your router.